Renaming Animation Channels with a Script
This should do the trick. Obviously, you will have to fill in the complete dictionary of bone name mappings.

import bpy

d = {"oldname1":"newname1","oldname2":"newname2", }
for action in bpy.data.actions:
    #these so called action groups are the bones, ie one group contains all fcurves of one bone
    for group in action.groups:
        if group.name in d:
            oldname = group.name
            group.name = d[oldname]
            for fcurve in group.channels:
                fcurve.data_path = fcurve.data_path.replace(oldname, d[oldname])